Carbon blacks may be utilized as pigments, fillers, reinforcing agents, and for a variety of other applications, and are widely utilized as fillers and reinforcing pigments in the compounding and preparation of rubber compositions and plastic compositions. Carbon blacks are generally characterized on the basis of their properties including, but not limited to, their surface areas, surface chemistry, aggregate sizes, and particle sizes. The properties of carbon blacks are analytically determined by tests known to the art, including iodine adsorption surface area (I2 No), nitrogen adsorption surface area (N2 SA), dibutyl phthalate adsorption (DBP), dibutyl phthalate adsorption of crushed carbon black (CDBP), cetyl-trimethyl ammonium bromide absorption value (CTAB) and Tint value (TINT).
Carbon blacks may be produced in a furnace-type reactor by pyrolyzing a hydrocarbon feedstock with hot combustion gases to produce combustion products containing particulate carbon black. A variety of methods for producing carbon blacks are generally utilized.
In one type of carbon black reactor, such as shown in U.S. Pat. No. 3,401,020 to Kester et al., or U.S. Pat. No. 2,785,964 to Pollock, hereinafter “Kester” and “Pollock” respectively, a fuel, preferably hydrocarbonaceous, and an oxidant, preferably air, are injected into a first zone and react to form hot combustion gases. A hydrocarbon feedstock in either gaseous, vapor or liquid form is also injected into the first zone whereupon pyrolysis of the hydrocarbon feedstock commences with consequent formation of carbon black. In this instance, pyrolysis refers to the thermal decomposition of a hydrocarbon. The resulting combustion gas mixture, in which pyrolysis is occurring, then passes into a reaction zone where completion of the carbon black forming reactions occurs.
Another type of process equipment utilized to produce carbon blacks is referred to as a modular or staged reactor. Modular (staged) furnace carbon black reactors are generally described in U.S. Pat. Reissue No. 28,974 and U.S. Pat. No. 3,922,355, the disclosures of which are hereby incorporated by reference.
In certain carbon black production processes a portion of the overall oxidant introduced in the process is introduced downstream of the point of feedstock injection. U.S. Pat. No. 4,105,750 discloses a process for producing carbon blacks with lower structure, as reflected by lower dibutyl phthalate (DBP) absorption numbers, for a given particle size. In the disclosed process a portion of the oxidant introduced in the process is injected at a location downstream of the point of feedstock injection.
WO 93/18094 discloses a process for producing carbon blacks characterized as adding a secondary oxidant stream to the reactor such that the secondary oxidant stream does not interfere with the formation of carbon black particles and aggregates in the reactor. In the disclosed examples the DBP absorption numbers of the carbon black produced utilizing the secondary oxidant stream were lower than the DBP absorption numbers of the carbon black produced utilizing the same reaction conditions in the absence of the secondary oxidant stream.
Other patents such as U.S. Pat. Nos. 3,607,058; 3,761,577; and 3,887,690 also describe the processes for producing carbon black.
The temperatures in a carbon black reactor can range between 2400° F. (1315° C.) and 3000° F. (1648° C.) or greater. The injection of additional oxidant, and/or secondary air into the reaction stream, for example, in the manner described in the aforementioned patents, will generally raise the temperature of the reaction stream, and may raise the temperature of the reaction stream in the region local to the point of air injection to well above 3000° F (1648°C.). This temperature extreme may cause damage to the refractory lining of the reactor and/or shorten the useful life of the refractory lining of the reactor, particularly near the area of additional oxidant injection.
Accordingly, it would be advantageous to have a method and apparatus for adding additional oxidant and/or hydrocarbon containing fluid streams into the effluent which minimized refractory problems in the reactor.
It would also be advantageous to have a method and apparatus for producing carbon blacks wherein the introduction of additional oxidant and/or hydrocarbon containing fluid streams into the effluent increased the structure of the carbon blacks produced by the process, as evidenced by the carbon blacks having an increased DBP absorption value for a given surface area.
The process and apparatus of the present invention achieve the aforementioned advantages in addition to other advantages that will become apparent to those of ordinary skill in the art from the following description.
Although general types of furnace carbon black reactors and processes have been described, it should be understood that the present invention can be used in any other furnace carbon black reactor or process in which carbon black is produced by pyrolysis and/or incomplete combustion of hydrocarbons.